using System.Collections.Specialized;

namespace Umbraco.Cms.Core.Models;

public class ContentScheduleCollection : INotifyCollectionChanged, IDeepCloneable, IEquatable<ContentScheduleCollection>
{
    // underlying storage for the collection backed by a sorted list so that the schedule is always in order of date and that duplicate dates per culture are not allowed
    private readonly Dictionary<string, SortedList<DateTime, ContentSchedule>> _schedule
        = new(StringComparer.InvariantCultureIgnoreCase);

    public event NotifyCollectionChangedEventHandler? CollectionChanged;

    /// <summary>
    ///     Returns all schedules registered
    /// </summary>
    /// <returns></returns>
    public IReadOnlyList<ContentSchedule> FullSchedule => _schedule.SelectMany(x => x.Value.Values).ToList();

    public object DeepClone()
    {
        var clone = new ContentScheduleCollection();
        foreach (KeyValuePair<string, SortedList<DateTime, ContentSchedule>> cultureSched in _schedule)
        {
            var list = new SortedList<DateTime, ContentSchedule>();
            foreach (KeyValuePair<DateTime, ContentSchedule> schedEntry in cultureSched.Value)
            {
                list.Add(schedEntry.Key, (ContentSchedule)schedEntry.Value.DeepClone());
            }

            clone._schedule[cultureSched.Key] = list;
        }

        return clone;
    }

    public bool Equals(ContentScheduleCollection? other)
    {
        if (other == null)
        {
            return false;
        }

        Dictionary<string, SortedList<DateTime, ContentSchedule>> thisSched = _schedule;
        Dictionary<string, SortedList<DateTime, ContentSchedule>> thatSched = other._schedule;

        if (thisSched.Count != thatSched.Count)
        {
            return false;
        }

        foreach ((var culture, SortedList<DateTime, ContentSchedule> thisList) in thisSched)
        {
            // if culture is missing, or actions differ, false
            if (!thatSched.TryGetValue(culture, out SortedList<DateTime, ContentSchedule>? thatList) ||
                !thatList.SequenceEqual(thisList))
            {
                return false;
            }
        }

        return true;
    }

    public static ContentScheduleCollection CreateWithEntry(DateTime? release, DateTime? expire)
    {
        var schedule = new ContentScheduleCollection();
        schedule.Add(Constants.System.InvariantCulture, release, expire);
        return schedule;
    }

    /// <summary>
    ///     Clears all <see cref="CollectionChanged" /> event handlers
    /// </summary>
    public void ClearCollectionChangedEvents() => CollectionChanged = null;

    /// <summary>
    ///     Add an existing schedule
    /// </summary>
    /// <param name="schedule"></param>
    public void Add(ContentSchedule schedule)
    {
        if (!_schedule.TryGetValue(schedule.Culture, out SortedList<DateTime, ContentSchedule>? changes))
        {
            changes = new SortedList<DateTime, ContentSchedule>();
            _schedule[schedule.Culture] = changes;
        }

        // TODO: Below will throw if there are duplicate dates added, validate/return bool?
        changes.Add(schedule.Date, schedule);

        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, schedule));
    }

    private void OnCollectionChanged(NotifyCollectionChangedEventArgs args) => CollectionChanged?.Invoke(this, args);

    /// <summary>
    ///     Adds a new schedule for invariant content
    /// </summary>
    /// <param name="releaseDate"></param>
    /// <param name="expireDate"></param>
    public bool Add(DateTime? releaseDate, DateTime? expireDate) => Add(Constants.System.InvariantCulture, releaseDate, expireDate);

    /// <summary>
    ///     Adds a new schedule for a culture
    /// </summary>
    /// <param name="culture"></param>
    /// <param name="releaseDate"></param>
    /// <param name="expireDate"></param>
    /// <returns>true if successfully added, false if validation fails</returns>
    public bool Add(string? culture, DateTime? releaseDate, DateTime? expireDate)
    {
        if (culture == null)
        {
            throw new ArgumentNullException(nameof(culture));
        }

        if (releaseDate.HasValue && expireDate.HasValue && releaseDate >= expireDate)
        {
            return false;
        }

        if (!releaseDate.HasValue && !expireDate.HasValue)
        {
            return false;
        }

        // TODO: Do we allow passing in a release or expiry date that is before now?
        if (!_schedule.TryGetValue(culture, out SortedList<DateTime, ContentSchedule>? changes))
        {
            changes = new SortedList<DateTime, ContentSchedule>();
            _schedule[culture] = changes;
        }

        // TODO: Below will throw if there are duplicate dates added, should validate/return bool?
        // but the bool won't indicate which date was in error, maybe have 2 diff methods to schedule start/end?
        if (releaseDate.HasValue)
        {
            var entry = new ContentSchedule(culture, releaseDate.Value, ContentScheduleAction.Release);
            changes.Add(releaseDate.Value, entry);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, entry));
        }

        if (expireDate.HasValue)
        {
            var entry = new ContentSchedule(culture, expireDate.Value, ContentScheduleAction.Expire);
            changes.Add(expireDate.Value, entry);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, entry));
        }

        return true;
    }

    /// <summary>
    ///     Remove a scheduled change
    /// </summary>
    /// <param name="change"></param>
    public void Remove(ContentSchedule change)
    {
        if (_schedule.TryGetValue(change.Culture, out SortedList<DateTime, ContentSchedule>? s))
        {
            var removed = s.Remove(change.Date);
            if (removed)
            {
                OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, change));
                if (s.Count == 0)
                {
                    _schedule.Remove(change.Culture);
                }
            }
        }
    }

    public void RemoveIfExists(string culture, ContentScheduleAction action)
    {
        ContentSchedule? changeToRemove = FullSchedule.FirstOrDefault(change =>
            change.Culture == culture
            && change.Action == action);
        if (changeToRemove is not null)
        {
            Remove(changeToRemove);
        }
    }

    public void AddOrUpdate(string culture, DateTime dateTime, ContentScheduleAction action)
    {
        // we need to remove the old one as ContentSchedule.Date is immutable
        ContentSchedule? changeToRemove = FullSchedule.FirstOrDefault(change =>
            change.Culture == culture
            && change.Action == action);

        if (changeToRemove is not null)
        {
            Remove(changeToRemove);
        }

        Add(new ContentSchedule(culture, dateTime, action));
    }

    /// <summary>
    ///     Clear all of the scheduled change type for invariant content
    /// </summary>
    /// <param name="action"></param>
    /// <param name="changeDate">If specified, will clear all entries with dates less than or equal to the value</param>
    public void Clear(ContentScheduleAction action, DateTime? changeDate = null) =>
        Clear(Constants.System.InvariantCulture, action, changeDate);

    /// <summary>
    ///     Clear all of the scheduled change type for the culture
    /// </summary>
    /// <param name="culture"></param>
    /// <param name="action"></param>
    /// <param name="date">If specified, will clear all entries with dates less than or equal to the value</param>
    public void Clear(string? culture, ContentScheduleAction action, DateTime? date = null)
    {
        if (culture is null || !_schedule.TryGetValue(culture, out SortedList<DateTime, ContentSchedule>? schedules))
        {
            return;
        }

        var removes = schedules.Where(x => x.Value.Action == action && (!date.HasValue || x.Value.Date <= date.Value))
            .ToList();

        foreach (KeyValuePair<DateTime, ContentSchedule> remove in removes)
        {
            var removed = schedules.Remove(remove.Value.Date);
            if (!removed)
            {
                continue;
            }

            OnCollectionChanged(
                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, remove.Value));
        }

        if (schedules.Count == 0)
        {
            _schedule.Remove(culture);
        }
    }

    /// <summary>
    ///     Returns all pending schedules based on the date and type provided
    /// </summary>
    /// <param name="action"></param>
    /// <param name="date"></param>
    /// <returns></returns>
    public IReadOnlyList<ContentSchedule> GetPending(ContentScheduleAction action, DateTime date) =>
        _schedule.Values.SelectMany(x => x.Values).Where(x => x.Date <= date).ToList();

    /// <summary>
    ///     Gets the schedule for invariant content
    /// </summary>
    /// <returns></returns>
    public IEnumerable<ContentSchedule> GetSchedule(ContentScheduleAction? action = null) =>
        GetSchedule(Constants.System.InvariantCulture, action);

    /// <summary>
    ///     Gets the schedule for a culture
    /// </summary>
    /// <param name="culture"></param>
    /// <param name="action"></param>
    /// <returns></returns>
    public IEnumerable<ContentSchedule> GetSchedule(string? culture, ContentScheduleAction? action = null)
    {
        if (culture is not null && _schedule.TryGetValue(culture, out SortedList<DateTime, ContentSchedule>? changes))
        {
            return action == null ? changes.Values : changes.Values.Where(x => x.Action == action.Value);
        }

        return Enumerable.Empty<ContentSchedule>();
    }

    public override bool Equals(object? obj)
        => obj is ContentScheduleCollection other && Equals(other);

    public static ContentScheduleCollection CreateWithEntry(string culture, DateTime? release, DateTime? expire)
    {
        var schedule = new ContentScheduleCollection();
        schedule.Add(culture, release, expire);
        return schedule;
    }

    public override int GetHashCode()
    {
        throw new NotImplementedException();
    }
}
